290 STRUCTURE AND CLASSIFICATION OF BIRDS 



some variation in the number of rings which coalesce to form 

 the box, while the fibrous continuation of the intrinsic muscles 

 may reach the first bronchial semi-ring. This muscle is 

 evidently decaying in Opisthocomus. 



GALLI ' 



Definition. Quintocubital birds with, an aftershaft. Muscles of leg 

 generally ABXY + . Expansor secundariorum present. Entepi- 

 condylo-ulnaris present. Caeca large ; a crop present. Skull 

 schizognathous, holorhinal, with sessile basipterygoid processes. 

 Palatines without internal lamina. 



This very large group of birds, universal in range, shows 

 a considerable amount of structural variation. 



The oil gland is generally tufted ; '-' but it is nude in the 

 Megapodes and absent altogether in Argus. 



The pterylosis of the Galli is, according to NITZSCH, 

 singularly uniform. He figures Gallus bankiva, Pavo 

 cristatus, and Meleagris gallo-pavo, describing also a few 

 other types. There are lateral neck spaces in all ; the dorsal 

 tract is single in Gallus, widening out on the back ; in the 

 peacock it widens out in a more pronounced fashion and 

 further back than in Gallus. In the turkey there is a 

 narrow space in it between the shoulder blades. 



The ventral tract divides early upon the neck, and each 

 tract gives off on the breast a wider, denser outer branch ; 

 the two median tracts then continue nearly to the cloaca, 

 where they unite. 



InPerdix and Tetrao there is a dorsal space, as in Meleagris. 



Among the Cracidse there may or may not be a space in 

 the dorsal tract. 



The pectoral muscles of gallinaceous birds, like those of 

 the tinamous, meet over the keel of the sternum ; this is at 

 least the case with Euplocamus Vieilloti and some others. 



1 H. SEEBOHM, ' An Attempt to Diagnose the Sub-Orders of the Great Galli- 

 naceo-Gralline Group of Birds by the Aid of Osteological Characters alone,' Ibis, 

 1888, p. 415. 



2 Callipepla calif arnica has a small tuft ; in C. squamata I have observed 

 both the complete absence of a tuft and the presence of a very small one. 



